1. Technical Field
The present invention relates to a measurement system, a measurement method, a robot control method, a robot, a robot system, and a picking apparatus.
2. Related Art
A phase shift method using a projector and a camera has been known as a method for measuring the three-dimensional shape of an object in a noncontact manner (see JP-A-2006-3212, for example).
In the phase shift method, in general, the projector projects a fringe pattern formed of a sinusoidal wave expressed by the magnitude of the luminance value toward an object to be measured, and the camera images the projected fringe pattern. In this process, the fringe pattern is projected four times with the phase of the projected fringe pattern shifted by π/2 each time, and the camera images the fringe pattern whenever projected. The luminance values in the same coordinates in the four captured images obtained by the four imaging actions are characterized in that the absolute value of each of the luminance values may change due, for example, to the surface state and the color of the object to be measured in the coordinates, but the relative value of each of the luminance values changes exactly by the amount corresponding to the difference in the phase of the fringe pattern. The phase value of the fringe pattern in the coordinates can therefore be determined in such a way that ambient light, the surface state of the object under measurement, and other factors less affect the phase value.
The phase values are first each determined, in the captured images, as a value that falls within the range from −π to +π for each fringe of the fringe pattern instead of a continuous value. The thus determined phase values are so processed in phase unwrapping as to be continuous values in the captured images. For example, in the system described in JP-A-2006-3212, the phase unwrapping is performed by using Fourier transform.
In the system described in JP-A-2006-3212, since the phase unwrapping is performed by using Fourier transform, it undesirably takes a long period to analyze captured images.